1. Technical Field
The present invention relates to a sheet processing apparatus for collecting sheets carried out from an image formation apparatus, etc. in the shape of a bunch for each set to perform processing such as binding and the like, and more particularly, to improvements in a sheet-bunch carrying-out mechanism that carries out a processed sheet bunch to a stack tray on the downstream side.
2. Description of the Related Art
Generally, this type of sheet processing apparatus is known as an apparatus for collecting sheets carried out from an image formation apparatus, etc. for each set, performing post-processing such as binding, punching processing, stamping processing and the like on the sheets, and storing the processed sheet bunch on a stack tray. Therefore, a processing tray is disposed on the downstream side of the sheet discharge path, the stack tray is disposed on the further downstream side, and sheets that are sequentially carried out to the processing tray are collected for each set and undergo post-processing in a stapling unit and the like. Then, the processed sheet bunch is stored on the stack tray coupled to a sheet discharge outlet of the processing tray.
For example, in Japanese Pat. Publication 2006-256729, a level difference is formed on the downstream side of the sheet discharge path to provide a processing tray, and in the processing tray are disposed a regulating stopper against which the sheet end is pushed to regulate, and a stapling apparatus for performing binding processing. Then, sheets carried out from the sheet discharge path are collected for each set in the processing tray, and the sheets are positioned by the regulating stopper, and bound by the stapling apparatus. Therefore, a bunch carrying-out mechanism is required which carries out a processed sheet bunch from the processing tray to the stack tray on the downstream side.
In the bunch carrying-out mechanism of above-mentioned Japanese Pat. Publication 2006-256729 is installed with a carrier member such as an endless belt or the like traveling along from one end to the other end of the sheet support surface of the processing tray, and the carrier member is provided with a sheet engagement member (sheet engagement pawl) to engage with the sheet rear end on the tray. Then, such a structure is adopted that the carrier member travels along the tray, and that the sheet rear end is thereby pushed out by the sheet engagement pawl to be carried out.
The sheet engagement pawl is not disclosed in Japanese Pat. Publication 2006-256729, but a pair of right and left sheet engagement pawls are disposed spaced apart from each other in the sheet width direction of the processing tray, and configured to push out a sheet bunch along the tray. Then, the sheet engagement pawls wait in a standby position (home position) spaced on the back side of the processing tray, and go forward in the sheet carrying-out direction from the standby position to engage with the sheet rear end edge after sheets are collected on the processing tray and undergo the post-processing. Then, it is configured that this bunch of sheets are carried out to the stack tray on the downstream side along the sheet support surface of the processing tray.
As described above, when a bunch of sheets collected on the tray are carried out to the stack tray on the downstream side, the carrying-out mechanism has conventionally been adopted that the sheet engagement pawls are moved from one end to the other end of the tray by an endless belt or the like. In this case, it is configured that the carrier member such as an endless belt, etc. and the sheet engagement pawls are integrally coupled, and that the sheet engagement pawls are moved to positions in the sheet carrying-out direction by travel of the belt. Then, the sheet engagement pawls turn or reciprocate along the sheet support surface of the processing tray.
In such a conventional bunch carrying-out mechanism, the carrier member such as an endless belt or the like and the sheet engagement pawls are integrally coupled. Then, the sheet engagement members are configured to wait to engage with the rear end edge of a bunch of sheets on the back side in the base end portion of the processing tray, while in the front end portion of the processing tray, delivering the sheets in a position protruding to the stack tray on the downstream side. Accordingly, there is the defect that the traveling stroke increases in the sheet engagement members, and that the apparatus thereby increases in size.
Further, the conventional sheet engagement pawls are formed of projection pawls that engage with the rear end edge of a bunch of sheets, thereby kick downward the bunch of sheets to the stack tray from the processing tray in delivering the bunch of sheets to the stack tray on the downstream side, do not enable bunches of sheets to be stacked and stored neatly on the stack tray, and are known as having the defect that the bunches are stored without being neatly aligned.
Therefore, it is desired that a bunch of sheets on the processing tray are gripped, pushed to be carried out, and landed without a level difference when the bunch of sheets are delivered to the stack tray. By this means, it is possible to prevent occurrence of problems such as creases, buckling and the like in moving a bunch of sheets along the processing tray, and concurrently, store bunches neatly on the stack tray.
The inventor of the present invention contrived the mechanism for gripping the rear end edge of a bunch of sheets to carry out in carrying out the bunch of sheets on the processing tray to the stack tray on the downstream side (for example, the Patent Application). Then, the inventor encountered the problem that the apparatus is increased in size when the grip mechanism is mounted on the carrier member such as a belt or the like.
Therefore, the inventor reached the idea that a sheet engagement member such as a grip mechanism or the like is installed in a carrier member such as a belt or the like to be able to move to positions in the bunch carrying-out direction, and that the sheet engagement member is stored in an attitude overlapping with the carrier member in an initial position for engaging with a bunch of sheets on the tray, and moves to a position protruding forward from the carrier member in a carrying-out position for carrying out the bunch of sheets to the stack tray.
It is an object of the invention to provide a sheet processing apparatus enabling a bunch of sheets to be neatly stored on a stack tray without a crease, buckling and the like occurring in the bunch of sheets in carrying out the bunch of sheets on a processing tray to the stack tray on the downstream side. Further, it is another object of the invention to provide a sheet processing apparatus enabling a small compact configuration of a bunch carrying-out mechanism for carrying out a bunch of sheets.